1. Field of the Invention
The invention relates to a springy contact element, according to the preamble claim 1, to be arranged between electrically conducting housing parts, in particular, between a plug-in housing and a mounting shaft.
2. Description of the Relevant Prior Art
Electronic devices such as measuring racks or computer units but also devices of the electronic entertainment sector such as, for example, a car radio, must be shielded sufficiently against electromagnetic interfering radiation. The shielding is conventionally achieved by grounding an electrically conducting housing wherein an exchangeable plug-in housing is connected by spring contacts with the ground of the mounting shaft. In this connection, the contact springs must ensure a reliable contacting even for repeated insertion and removal of the plug-in housing.
A contact element of the aforementioned kind is known from DE 195 07 846 C1. The housing part, comprised of a sheet metal that can be shaped, of the plug-in housing or of the mounting shaft has a sheet metal tab formed as a unitary part out of a slot of the sheet metal which, for forming the springy contact element, is reduced by cold forming relative to the thickness of the sheet metal. In this connection, the contact spring is of a wavy shape across its length wherein an individual wave projects arc-like from the plane of the sheet metal. Since the contact element is secured by a base portion on the narrow side of the slot and the wavy shape provides a longitudinal shortening, the contact element, when greatly loaded, penetrates through the slot and, in this connection, an elastic deformation can occur which disturbs reliable contacting. It is therefore also suggested to support the contact spring with its free end on the narrow side of the slot. However, this impairs the shaping because only a minimal longitudinal shortening by shaping is permissible.
It is an object of the invention to configure a springy contact element of the aforementioned kind such that a high spring stiffness results for a free selection of the shape.
The object is solved according to the invention by the support area of the contact element having correlated therewith a support surface of the sheet metal which extends transversely to the longitudinal tab axis away from the longitudinal slot edge and which engages underneath the support area.
The support surface of the sheet metal correlated with the support area of the contact element extends transversely to the longitudinal tab axis away from the longitudinal edge of the slot so that a support action for the contact element is realized on a configurationally selectable point of the longitudinal edge of the slot. Accordingly, across the entire length of the slot, independent of the shortening resulting from the shaping of the contact element, a reliable support action can be selected which ensures a torsion-free receiving of forces by the contact element. Advantageously, the support surfaces of the sheet metal on the longitudinal tab edges of the slot are positioned at a spacing opposite one another so that to the left and to the right of the longitudinal tab axis at the edge of the slot a support action is provided. A torsion of the contact element formed by the sheet metal tab about the longitudinal tab axis is thus reliably prevented.
Advantageously, the support area at the free end of the sheet metal tab is formed so that its entire length can contribute to the spring properties of the contact element.
Expediently, the greatest width of the support area before cold forming can be slightly greater than the spacing of the support surfaces; this can be achieved, for example, in that the free end is realized with a greater width than the remaining sheet metal tab. Preferably, the support area receives the required width by cold forming in order to rest against the support surfaces of the sheet metal positioned approximately opposite one another at a spacing transversely to the longitudinal slot axis.
When the free end of the sheet metal tab in plan view is formed by cold forming to a disk shape, it is expedient to bend the disk-shaped end approximately about a diameter which is transversely positioned to the longitudinal slot axis so that the disk-shaped end becomes stiffer and can thus dissipate high support forces onto the support surfaces without deformation.